Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753401AbdGJGNV (ORCPT ); Mon, 10 Jul 2017 02:13:21 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:9293 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750969AbdGJGNU (ORCPT ); Mon, 10 Jul 2017 02:13:20 -0400 Subject: Re: [PATCH RESEND] arm64: arch_timer: fix the infinite recursion when enable ftrace and erratum workaround To: Ding Tianhong , Mark Rutland , Marc Zyngier , Catalin Marinas , Will Deacon , LinuxArm , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" References: <321e4c16-aa14-beee-b6dc-36e19e5ec35a@huawei.com> From: Hanjun Guo Message-ID: <59631ACD.4020103@huawei.com> Date: Mon, 10 Jul 2017 14:12:29 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <321e4c16-aa14-beee-b6dc-36e19e5ec35a@huawei.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.17.188] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020201.59631AF4.00A3,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2014-11-16 11:51:01, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: c4160f1e7887b810375d53f5b7b054c2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1909 Lines: 49 On 2017/7/9 16:30, Ding Tianhong wrote: > When enable preempt and debug ftrace, and perform the following steps, the > system will hang: > mount -t debugfs nodev /sys/kernel/debug/ > cd /sys/kernel/debug/tracing/ > echo function_graph > current_tracer > > This is because tracing the preempt_disable/enable calls would cause > trace_clock() which would get local timer to go into infinite recursion > when enable the arch timer erratum workaround for some chips, so Prevent > tracing of preempt_disable/enable() in arch_timer_reg_read_stable(). > > This problem is similar to the fixed by upstream commit 96b3d28bf4 > ("sched/clock: Prevent tracing recursion in sched_clock_cpu()"). > > Fixes: 6acc71ccac71 ("arm64: arch_timer: Allows a CPU-specific erratum to only affect a subset of CPUs") > Signed-off-by: Ding Tianhong > --- > arch/arm64/include/asm/arch_timer.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h > index 74d08e4..67bb7a4 100644 > --- a/arch/arm64/include/asm/arch_timer.h > +++ b/arch/arm64/include/asm/arch_timer.h > @@ -65,13 +65,13 @@ struct arch_timer_erratum_workaround { > u64 _val; \ > if (needs_unstable_timer_counter_workaround()) { \ > const struct arch_timer_erratum_workaround *wa; \ > - preempt_disable(); \ > + preempt_disable_notrace(); \ > wa = __this_cpu_read(timer_unstable_counter_workaround); \ > if (wa && wa->read_##reg) \ > _val = wa->read_##reg(); \ > else \ > _val = read_sysreg(reg); \ > - preempt_enable(); \ > + preempt_enable_notrace(); \ > } else { \ > _val = read_sysreg(reg); \ > } \ This fixes my system hang issue when I using function tracer with enabled timer errata on D03, Tested-by: Hanjun Guo Thanks Hanjun